1. Field of the Invention
This invention relates generally to a cooling water pump seal for a combustion engine. More particularly, this invention relates to a cooling water pump seal having a main seal that rests on a shaft with a sliding fit and a protective seal fastened to the housing that supports the main seal.
2. The Prior Art
A cooling water pump seal in which a protective rubber seal forms an integral part of a rubber main seal is disclosed in U.S. Pat. No. 4,155,560. This and other prior art cooling water pump seals, however, suffer from disadvantageously short service lives. This problem encountered in employing prior art cooling water pump seals in a combustion engine is attributable in part to the stress imposed upon the main seal by the protective seal. A further problem encountered in using prior art cooling water pump seals in combustion engines is thermal loading of the seal during use. This thermal loading problem is particularly acute in the dynamic sealing zone of prior art seals. Abrasive particles present in coolants, such as rust particles or sand, also contribute to the unsatisfactory service life of cooling water pump seals disclosed in the prior art.